A sliding contact guide can be in the form of a fixed guide, or a pivoted tensioner lever. In a typical tensioner lever, a synthetic resin shoe, having a surface on which a chain or other transmission medium can slide, is connected to a supporting arm. The lever assembly, consisting of supporting arm with the shoe attached to it, rotates about a pivot shaft fixed to an engine block and projecting through a hole formed adjacent one end of the supporting arm. The supporting arm is engaged, at a location remote from the pivot axis, by the plunger of a tensioner, the housing of which is also fixed to the engine block.
FIGS. 7 and 8 show a typical tensioner lever 500, in which plural L-shaped protrusions 511 are provided along one long edge of an elongated shoe 510 for connecting the shoe to an elongated supporting arm 520. Plural strip-shaped protrusions 512 are provided along the other long edge of the shoe, and a U-shaped hook 513, formed at one end of the shoe, engages the end of the arm adjacent the pivot axis. Thus, the hook 513 is located at the end of the tensioner lever which the transmission medium approaches as it travels from a driving sprocket toward the lever. The L-shaped protrusions 511, the strip-shaped protrusions 512, and the hook 513, prevent the shoe from floating with respect to the supporting arm 520. The typical tensioner lever shown in FIGS. 7 and 8 is also described in U.S. Pat. No. 5,184,983.
FIGS. 9 and 10 show a typical fixed guide 600, also known as a “guide rail,” in which a shoe 610 is engaged with a support 620. The shoe has a hook-shaped end 611, which engages an end 621 of the support 620 at a location at which the guide is approached by a transmission medium as the medium travels from a driven sprocket toward the guide. L-shaped elements 612 are formed along both long edges of the shoe for attachment of the shoe to a flange 622 of the support. This typical fixed guide is described in Japanese Utility Model Publication No. Hei.-36201, and a similar fixed guide is described in U. S. Pat. No. 5,045,032.
In the case of the tensioner lever 500 as shown in FIGS. 7 and 8, in which the shoe is held on the support by a combination of the U-shaped hook 513, L-shaped protrusions along only one long edge of the shoe, and strip-shaped protrusions along the other long edge of the shoe, the shoe 510 is liable to disengage from the arm 520 in operation. Since the shoe 510 is formed of synthetic resin, it undergoes repeated elongation and shrinkage due to temperature changes, especially when used in the timing drive of an engine. The elongation of the shoe can cause a gap to form between the shoe 510 and the arm 520. Because of the gap, the shoe 510 can move longitudinally relative to the supporting arm, and this longitudinal movement can allow the U-shaped end hook 513 to become disengaged from the arm.
In the case of the fixed guide 600 in FIGS. 9 and 10, the L-shaped elements 612 on one edge of the shoe are nearly opposite those on the other edge. Consequently, it is difficult to connect the shoe 610 with the flange 622 of the support arm during assembly of the tensioner lever.
The principal object of this invention is to solve the above-mentioned problems. More specifically, the invention provides a guide in which the shoe and the shoe support can be easily connected to each other during assembly of the guide. A secure connection between the shoe and the support is provided so that disengagement of the shoe from the support during operation can be avoided, and stable travel of the transmission medium is ensured.